Escort memory device



1964 M. J. PRUCHA ETAL 3, 57,270

ESCORT MEMORY DEVICE Filed NOV. 26, 1962 2 Sheets-Sheet 1 F/G.2 F7613 .INVENTORS MART/N JOHN PRUOHA By ROBERT A. BOUOR/AS ATTORNEY United States Patent 3,157,270 ESCORT MEMORY DEVICE Martin John Prucha and Robert A. lloudrias, Palo Alto,

Calif., assignors to General Precision, Inc., Binghaniton, N.Y., a corporation of Delaware Filed Nov. 26, 1962, Ser. No. 240,769 9 Claims. ((31. 1198-38) This invention relates to memory and control devices associated with conveyor buckets for storing coded information to cause the buckets to discharge the articles at selected locations. This invention is an improvement of a conveyor memory and control arrangement generally shown and described in a co-pending United States patent application, Serial No. 78,538, entitled Conveyor Sorting, filed by Robert A. Kleist on December 27, 1960, now Patent No. 3,100,040, and assigned to the same assignee as the instant application. The instant patent application is a continuation-in-part of an application, Serial No. 102,150 filed April 11, 1961 now abandoned.

Conveyors are commonly used for transporting articles, and a conveyor may include a plurality of holders or trays especially adapted to contain and carry the articles. These special holders are commonly called buckets, and for the purposes of this patent application, the term bucket will denote such a holder on a conveyor. The memory and control device of this invention is adapted to be mounted on and carried by a conveyor bucket. Since this device functionsdo control the operation of the bucket with which it moves, it may be denoted as an escort memory device.

The application of Robert A. Kleist, supra, shows and describes an arrangement of primary and secondary conveyors for receiving and selectively discharging articles such as mail. A postal clerk or other operator may key digital information indicative of a sorting destination for each successive article of mail, and then may place the article upon a primary conveyor. In response to the keyed sorting instruction, the primary conveyor will carry and discharge the article into a selected one of several secondary conveyors; and in further response to the sorting instructions, the secondary conveyor will carry and discharge the article at a selected one of several possible discharge locations.

The sorting instructions keyed by the operator become digitally coded signals which are entered into escort memory devices attached to and movable with the buckets of the conveyor system. The memory devices may be in the form of magnetic bodies, preferably small bar magnets, shiftably mounted on the buckets. When reset, each of the magnets will be in a first position with respect to the bucket, and a reset pattern or configuration of magnets is produced. When coded information is entered, one or more selected magnets are shifted to a second position and a modified pattern of magnets thus produced is indicative of the coded information. The application of Robert A. Kleist, supra, discloses magnets shiftable longitudinally, the aXis of which motion is parallel to the direction of movement of the conveyor, and a reset was accomplished by a fast moving magnetic device or magnetic field which would draw all of the magnets forwardly with respect to the movement of the conveyor.

It is an object .of this invention to provide an improved escort memory device which is simple to set and rese and which will be particularly stable and immune to disturbing effects caused by vibrations and accelerations which may be inherent in a conveyor system.

It is a further object of this invention to provide an improved escort memory device which is economical in construction and operation; and more, specifically, it is an object to provide such a device having magnetic bodies which may be pivoted about a fulcrum from a first stable position to a second stable position to minimize frictional drag and to reduce inertia eifects such that less energy will be required to set each mass into rotational motion from an initial stable position than would be required to set a corresponding mass into linear motion to cause translation of the body.

It is another object of this invention to provide an improved escort memory device including a magnetic body which may be pivoted from one stable position to a second stable position, and vice versa, by stationary magnetic means positioned adjacent to the conveyorsaid stationary magnetic means being a permanent magnet or an electromagnet which may selectively set or reset the memory device without moving parts or moving magnetic elds.

A further object is to provide an improved memory device for a conveyor wherein a magnetic body may move between two stable positions, and more particularly, it is an object to provide a resilient magnetic holding means in the form of ferrite material impregnated neoprene rubber or a like substance such that the magnetic body will be held against a relatively soft cushion and may be moved from one stable position to the other quietly without undue vibration and without subjecting the magnetic body to shock with each movement thereof.

Numerous other objects and advantages will be ap parent throughout the progress of the specification which follows. The accompanying drawings illustrate certain selected embodiments of the invention and the views therein are as follows:

FIGURE 1 is a perspective view illustrating a memory device of this invention;

FIGURE 2 is a plan view of the device of FIGURE 1 with a cover plate removed exposing the underlying parts;

FIGURE 3 is a view similiar to FIGURE 2 illustrating a modified form of this invention;

FIGURE 4 is a view similar to FIGURES 2 and 3 illustrating yet another form of this invention;

FIGURE 5 is a horizontal sectional view of a conveyor arrangement of this invention looking along the plane 55 of FIGURE 6, and illustrating the operation of an escort memory device in accordance with this invention; and

FIGURE 6 is a vertical sectional View of the conveyor arrangement looking along the plane 6-6 of FIGURE 5.

Briefly stated, according to this invention, an escort memory device for a conveyor includes one or more magnetic bodies mounted to pivot from a first stable position to a second stable position. The magnetic body is prefthe ends of the bar magnet at the extremes of its pivotal travel, and therefore, the magnet 12 will remain in either of the two stable positions until an external magnetic field appears and overcomes the holding means.

A shown in FIGURES 1 and 2 the magnetic holding means may constitute a pair of angular plates or members 15 and 15' of a metal which has a moderate magnetic permeability. In FIGURE 3 the magnetic holding means constitutes a pair of magnetic plates or members 16 and 16' which may be of soft iron or other highly permeable magnetic material, but which is embedded in the nonmagnetic material of the housing 14 to prevent close contact with the ends of the bar magnet 12. In FIGURE 4, the magnetic holding means includes a pair of angle sheets 3 17 and 17' of permeable material positioned such that a small end surface is near the end poles of the magnet 12.

The three embodiments of this invention shown by FIGURES 2, 3 and 4 each includes the housing 14 of nonmagnetic material with the cavity 13 therein, and in each case the narrow mid portion of the cavity 13 includes two opposed spaced fulcrum angles 18 providing points about which the bar magnet 12 may pivot. The embodiment of FIGURES 1 and 2 provides an advantage in that the sheets of angle material 15 and 15' may be metallic and are positioned to receive all wear resulting from contact with and movement of the magnet 12. However the pole ends of the magnet 12 will lie directly against the angle sheets 15 and 15', and if these be of a highly permeable material such as steel, the resulting retaining force holding the magnet in the extreme positions will be so great that a very large external magnetic force will be necessary to overcome that holding force. Therefore, the sheets 15 and 15 may be fabricated from a material which has a moderate magnetic permeability, and will therefore exert only a moderate holding force upon the magnet 12.

The sheets 15 and 15 of FIGURES 1 and 2 may be of a neoprene rubber or like substance having a ferrite material impregnated therein. The ferrite material will provide the elements 15 and 15 with magnetic properties for holding the magnet 12 in either of the two extreme posi tions, and therefore, the two stable states representative of a binary one and a binary zero will be established. The neoprene or like material will cushion the magnet 12 to absorb and minimize the jarring or shock as the magnet shifts from one stable position to the other. Since the shock or pounding of the magnets is minimized, the operation of each memory device will be smoother and quieter. In this case, the structure of the housing 14 may be made smaller and less massive since it will not be exposed to shock or pounding. Furthermore, there will be no tendency for the permanent magnet 12 to loose its strength due to the constant pounding to which it would otherwise be subjected. It will therefore be appreciated that a memory device using ferrite impregnated neoprene cushions will be quieter in operation and superior in construction.

In the event that the material of the holding plates is to be fabricated from soft iron or the like, the construction illustrated by FIGURES 3 or 4 will be more feasible. In each case, the pc le ends of the magnet 11 are held somewhat apart from the holding plates 16-16 or 17-17, and the resultant magnetic holding force will not be unduly great. Satisfactory magnetic holding means may be provided by other arrangements than those specifically illustrated.

The magnetic memory device shown in FIGURES 1 through 4 are capable of storing one binary bit of information since it is capable of existing in either of two stable states which may be representative of the binary digits and 1. A practical application of this invention would, no doubt, require that the escort memory devices be capable of storing more than a single bit of information, and therefore, a plurality of such devices may be attached to each bucket of a conveyor. FIGURES and 6 illustrate the method of encoding and decoding information from a memory having a capacity of two binary bits. Most practical applications of this invention would require an even greater bit capacity which may be obtained by additional binary devices associated with each of the conveyor buckets. However, the encoding and decoding method of this invention may be understood by considering a two bit system and further extensions will be obvious.

As shown by FIGURE 6, the shiftable magnets 12 are positioned Within cavities which may be part of conveyor buckets which are moving from left to the right as indicated by the arrows therein. The buckets move above a stationary structure or rail 19, and at a first location permanent bar magnets21 are mounted flush with the rail and constitute a reset station. The buckets 20 will carry memory devices including the shiftable magnets 12 into closed spaced relation over the stationary bar magnets 21. As indicated by FIGURE 5 the bar magnets 21 located at the reset station 22 are positioned diagonally with respect to the movement of the conveyor and are orientcd at a predetermined angle B with respect to :1 reference line 23 extending perpendicular to the direction of movement of the conveyor. As the bucket appears at a location 2%) and approaches the reset station 22, the shiftable magnets 12 and 12 may be in either of the stable positions but are oriented at an angle a with respect to a line 24 normal to the conveyor direction and parallel with the line 23. As the memory devices and magnets 12 and 12' move directly over the reset magnets 21, the pole ends of the stationary magnets 12 and 12 are similarly oriented with the respective north poles and south poles being brought into close proximity with each other. The angle ,8 is somewhat greater than the angle a and therefore, the magnetic repulsion forces acting will cause the shiftable magnets 12 and 12 to pivot to an orientation approximately at right angles with the magnets 21. After the bucket has moved past the reset station 22, the magnets 12 and 12 are reset to a first stable position as indicated at location 20. The first stable position may be arbitrarily considered to be a binary 0, while the initial positions of the magnets as shown at the location 20 may be arbitrarily considered to be the binary l. The magnets 21 of the reset station 22 will cause the magnets 12 and 3.2 to assume the position representative of the binary O regardless of the prior position at the conveyor location 20.

As the conveyor continues to move, the bucket will pass from the location 29 over an input station 25 to a further location 2t)". The input station 25 includes a plurality of electromagnets 26 and 26 which may have a U-shaped core structure with pole faces extending upwardly and flush with the rail 19. As indicated in FIGURE 5, the electromagnets may be coupled to a direct current power source 28 via an encoding circuit means indicated in FIG- URE 5 as simple switches 29 and 30. The switch 29 is indicated as being closed causing the magnet 26 to be energized whereupon north and south magnetic poles will appear oriented at the angle ,8 with respect to a transverse line 31. On the other hand, the switch 30 is indicated as being open such that the magnet 26' will not be energized. As the conveyor bucket passes from position 20' to position 23 the shiftable magnet 12 will be carried into close proximity with the energized electromagnct 26 such that magnetic repulsion forces will cause the magnetic body 12 to shift from the first stable position to the second stable position thereby indicating a binary 1 bit stored in the device. On the other hand, as the magnetic body 12' passes into close proximity with the magnet 26 no magnetic forces will appear since the switch 30 is open and the magnet 26' is not energized. Therefore, when the bucket appears in the position 29" the magnetic body 12 will be set in a 1 position while the magnetic body 12 will remain in the 0 position. It may be appreciated that the binary number 10 (decimal number 2) will have been entered into the escort memory.

After the conveyor bucket has passed the input station, it may approach a succession of output stations. Each of the output stations includes a plurality of mag netic switches which are normally open, but which close when subjected to a magnetic gradient between the opposite ends thereof. Each switch contains a pair of elements which will become oppositely polarized to attract each other when a magnetic field is applied. Thus, in the presence of a magnetic field the natural resiliency of the elements is overcome, whereupon the switch closes and energizes an electrical circuit coupled thereto. After the magnetic field has beene removed, the natural resiliency of the elements cause themselves to spring apart thereby opening the switch and tie-energizing the associated elec trical circuit. Magnetic switches of this type are sold commercially under the trade name of Clareed by the C. P. Clare and Co., 3101 Pratt Blvd, Chicago 45, Illinois.

The first output station ill is so designated because a first magnetic switch 33 is aligned to correspond with the reset or position of the magnet 12. While the second of the magnetic switches 34 is aligned, in accordance with the set or 1 position of the shiftable magnet 12'. If the magnets 12 and 12' are positioned as shown at 2th", the magnetic fields therefrom will be at right angles with the switches 33 and 3dand will not generate a properly aligned magnetic gradient for operation of the switches. Therefore, as the bucket passes over the output station ill, no signal will be generated or passed to an actuation circuit 35.

As shown in FIGURE 5 the next subsequent output station It) is so designated because a first of the magnetic switches 36 is aligned in accordance with the set or 1 position of the magnet 12 while the second switch 37 is aligned in accordance with the reset or 0 position of the magnet 12. In this case, the orientation of the switches 36 and 37 corresponds with the positioning of the magnets 12 and 12 as the bucket moves from the position 253" across the output stations. In this case, both the switches 36 and 37 will simultaneously close, and since they are connected in series with each other and with a voltage source 33, a voltage pulse will be passed to an actuation circuit 39. The actuation circuit may in its simplest form he a solenoid for the operation of a magnetic device (not shown) which may be positioned adjacent to the conveyor near the output station and may cause the bucket to discharge its load at that point. Since the voltage pulse passed by the switches 36 and 37 may be of limited value and duration theactuation circuit may preferably take the form of a relay (either magnetic or electronic) such that the pulse merely functions to initiate further operations which may require a timed duration and energy input beyond the capabilities of the magnetic switches 36 and 37. A preferred form of an actuation circuit has been disclosed in the co-pending patent application of R. A. Kleist, supra, and includes among other components, a pulse generator or monostable multivibrator circuit which may betriggered by the short duration voltage pulse passed by the switches 36 and 37, and which will generate a longer duration output pulse capable of furnishing sufficient energy to drive a solenoid circuit.

FIGURE 5 further shows an actuation station 11 so designated because both the magnetic switches 4t? and 41 are aligned to correspond with the set or 1 position of the magnets 12 and 12'. Thus, if the conveyor bucket moves from the position 20" over the output station 11, the magnetic switch 40 would close, but the magnetic switch 41 would remain open and no voltage pulse would be supplied to an actuation circuit 42. From the foregoing it will be appreciated that an operator at the input station 25 may selectively set or key switches 29 and 3t) which will ultimately control the discharge operation of a conveyor bucket. The escort memory device attached to and carried by the conveyor bucket is first reset at the station 22 and thence is selectively set with digital information at the station 25 in accordance with the selected closure of the switches 29 and 3d. After being selectively set, the escort memory device will pass a sequence of output stations and will cause the operation of an actuation circuit at a selected output station in accordance with the digital information set therein.

It may be appreciated that the magnets 12 and 12' may be shifted by magnetic forces of either attraction or repulsion. If it were intended to operate the memory devices by magnetic attraction, the north and south poles of the reset magnets 21 and of the selective set magnets 26 and 26' would be aligned with the respective south and north poles of the magnets 12 and 12. However, the use of repulsion forces as heretofore described,

is deemed to be advantageous since a maximum force is applied to the shiftable magnets 12 and 12 to initiate the movement thereof. This maximum force will overcome the holding force of the bistable device and will set the magnets I2. and 12' into pivotal motion. After the magnets 12 and 12' are in motion, it is of little consequence that the magnetic forces will decrease in value, since the inertia of the magnetic body will continue its movement until the second stable position has been reached.

A magn tic memory device has been constructed and successfully operated in accordance with the teachings of this invention wherein the pivotal angle a was established to be 45 on both sides of the center line 24 extending normal to the direction of conveyor movement. In this case, the angle {3 was established at 50 from the normals 23 and 31. When the magnets 12 and 12' of the memory device are moved over the stationary magnets 21 or 2213-26, the fact that the angle [3 is slightly greater than the angle a will cause the shiftable magnets 12 and 12 to be repulsed and moved in the proper direction for the setting and resetting operations. The 45 value for the angle on is optimum for the operation of the magnetic switches such as 33 and 34 since a maximum magnetic gradient will be applied to the switch for closure thereof when the magnet 12 is properly aligned, but a substantially zero magnetic gradient will be applied to the switch when the magnet 12 is in the non-operating position. Therefore, with a 45 alignment the switches $3 and 34 etc. have a maximum reliability of operation.

It has been proposed that the angle at may be somewhat reduced to a value of 35 to 40 whereby the pivotal deflection or excursion of the magnets 12 will be decreased witha resultant saving in the energy which may be required for the setting and resetting operations. In this event the angle a would be correspondingly decreased such that it will continue to be slightly greater than the reduced angle a.

Itis proposed that the magnets 12 and 12 have a circular cross section and be cylindrical in shape. A cylindrical magnet is less prone to becoming wedged or jammed within the cavity 13 and will pivot around the fulcrum points It; with greater ease. In a practical appli cation of this invention, the memory devices will probably require a capacity from 5 to 12 bits for data storage permitting. a substantial number of selective output stations. In such an arrangement, it may be desirable to miniaturize the magnets to conserve space on the conveyor bucket and to provide a reasonable pattern of magnets. Miniaturization may be best accomplished with small cylindrical permanent magnets.

FIGURE 4 shows a magnetic holding means including angle plates 17 and I7 and including further obliquely positioned magnetic member 44 and 44. These members andd 'l may function as temporary magnetic field shunts to reduce the apparent field strength of the stationary'magnet during times immediately prior to and immediately following the set and reset operations of the magnet 212. If we consider the structure of FIGURE 4 to be moving with the conveyor from left to right, and moving across a fixed diagonal magnet, the magnetic member t s'first comes into alignment and effectively reduces the etiective field to prevent spurious operation or movement of the shiftable magnet 12. Asthe structure of FIGURE 4 to continues to move to the right the fixed magnet will come into close proximity with the magnet 12, and the repulsion forces induced therein will cause the magnet 12 to shift to a position indicated by dashed lines 45. Subsequently, the structure of FIGURE 4 will continue to move the right and the fixed magnet will become aligned with the member 44 which will act as a field shunt to reduce the effective field strength of the magnet, and will prevent further shifting of the magnet 12. As the structure of FIGURE 4 continues to move to the right it leaves the field of the fixed magnet will have no further effect thereon.

In this invention, each magnetic switch is operated only when the shiftable magnet 12 of the escort memory device is in proper alignment with the switch. This may be expected to occur approximately 50% of the times when bucket passes each output station. During those times when the shiftable magnet 12 is perpendicular to the magnetic switch, no operation thereof will occur. This fact will effectively double the life of each of the magnetic switches and will provide an advantage over other arrangements wherein the magnetic switch is operated each and every time that a bucket passes thereover.

As shown and described heretofore, the magnets 12 are shiftable between two stable positions each of which is at the angle at approximately 45 with the transverse centerline 24-. An obvious alternative would be to rotate each of the cavities 13 through a 45 angle such that the two stable positions of the magnet 12 would be either aligned axially in the direction of conveyor travel or aligned transversely across the direction of conveyor travel. Such an arrangement would prove advantageous in that the reset magnets 21 and the selected set magnets 26 and 26 could be positioned longitudinally or transversely with the conveyor. Likewise, the pattern of the magnetic switches 33, 34 etc. would be aligned longitudinally and transversely with the conveyor.

As shown and described heretofore the input station 25 utilizes an electromagnet which may be selectively energized to set bit information into the escort memory device. An obvious alternative would be provide permanent magnets which are movable vertically into a flush position with respect to the conveyor rail 19. These magnets is a retracted position will have no effect on the escort memory devices, but when selectively moved to the flush position at the conveyor will enter bit information into the memory devices.

Changes may be made in the form, construction and arrangement of the parts without departing from the spirit of the invention or sacrificing any of its advantages, and the right is hereby reserved to make all such changes as fall fairly within the scope of the following claims.

The invention is claimed as follows:

1. A memory system for a conveyor comprising a magnetic body mounted on the conveyor rotatable between a first stable position and a second stable position, means associated with each pair of said stable positions for applying a force to their associated magnetic body to tend to maintain said magnetic body in one or the other of said stable stable positions, means positioned in spaced relation to the conveyor for magnetically co-acting with and for selectively causing the magnetic body to shift from the first stable position to the second stable position, and sensing means positioned in spaced relation with the conveyor for sensing the magnetic body in the second stable position.

2. A memory system for a conveyor comprising a plurality of magnetic bodies mounted on the conveyor and each rotatable between a first stable position and a second stable position, means associated with each pair of said stable positions for applying a force to their associated magnetic body to tend to maintain said magnetic body in one or the other of said stable positions, means positioned in spaced relation to the conveyor for magnetically co-acting with and for causing selected ones of the magnetic bodies to shift from the first stable position to the second stable position, and a plurality of sensing means positioned in spaced relation with the conveyor for generating an actuation signal by sensing that selected ones of the magnetic bodies are in the second stable position.

3. An escort memory system for buckets of a conveyor comprising a plurality of magnetic bodies mounted on each of the buckets and rotatable between a first stable position and a second stable position, means associated with each pair of said stable positions for applying a force to their associated magnetic body to tend to maintain said magnetic body in one or the other of said stable position, stationary means positioned in spaced relation with the conveyor for magnetically co-acting with and causing selected ones of the magnetic bodies to shift from the first stable position to the second stable position, and a plurality of sensing means positioned in spaced relation with the conveyor for generating an actuation signal by sensing a predetermined magnetic pattern established when selected ones of the magnetic bodies are set in the second stable position.

4. An escort memory system for receiving digital infornvtion and for controlling the operation of a bucket of a conveyor in accordance therewith, said system comprising a housing attached to and carried by the conveyor, said housing having a plurality of cavities therein, each of the cavities having oppositely spaced arcuate end lobes and having a reduced center portion, an elongated magnetic body positioned within each of the cavities and operable to pivot about fulcrum points established by the reduced center portion of the cavity, and magne 'c means positioned adjacent to the conveyor such that each cavity with the magnetic body therein will pass in close spaced relation with said magnetic means, said magnetic means being operable to shift selectively and to pivot the magnetic body about the fulcrum points and through the arcuate end lobes of the cavity from one stable position to another.

5. Escort memory apparatus for receiving digital in formation and for controlling the operation of a bucket of a conveyor in accordance therewith, said apparatus comprising a housing attached to and carried by the conveyor, said housing having a plurality of cavities therein, each of the cavities having oppositely spaced arcuate end lobes and having a reduced center portion, an elongated magnetic body positioned within each of the cavities and operable to pivot about fulcrum points established by the reduced center portion of the cavity, said housing including magnetic holding means positioned in spaced relation with each of the cavities for establishing two stable positions wherein the magnetic body will be held, and magnetic means positioned adjacent to the conveyor such that the magnetic bodies will pass in close spaced relation therewith, said magnetic means being operable to selectively overcome the magnetic holding means and to pivot the body about the fulcrum points from one stable position to the other.

6. Escort memory apparatus for receiving digital information and for controlling the operation of a bucket of a conveyor in accordance therewith, said apparatus comprising a housing attached to and carried by the conveyor, said housing having a plurality of cavities therein, each of the cavities having oppositely spaced arcuate end lobes and having a reduced center portion, plates formed from magnetic material spaced along the sides of each of the cavities and forming angles on opposite sides of the reduced center portion for providing fulcrums, and an elongated magnetic body positioned within each of the cavities and pivotal about the fulcrums, said plates of magnetic material further providing a holding means for establishing two stable postions of the magnetic body with each cavity.

7. Escort memory appartus for receiving digital information and for controlling the operation of buckets of a conveyor in accordance therewith, said apparatus comprising a housing attached to and carried by each bucket of the conveyor, said housing having a plurality of cavities therein, each of the cavities having oppositely spaced arcuate end lobes and having a reduced center portion, an elongated magnetic body positioned within each of the cavities and pivotal about the reduced center portion such that the ends of the magnetic body will swing through the arcuate end lobes of the cavity, members formed from magnetic material positioned in spaced relation with the end lobes of each cavity operable to tagnetically hold the magnetic body for establishing two stable positions thereof, magnetic means in a fixed position in spaced relation with the conveyor for selectively shifting each magnetic body from one stable position to the other in response to the received digital information, and a further magnetic member positioned in spaced relation with each cavity for providing a magnetic shunting means to reduce the field strength of the fixed magnetic means and to prevent spurious shifting of the magnetic body therein.

8. A memory device for a conveyor comprising a housing attached to and carried by the conveyor, said housing having a cavity therein, said cavity having oppositely spaced arcuate end lobes and a reduced center portion, and an elongated magnetic body positioned Within the cavity and operable to pivot about fulcrum points established by the reduced center portion of the cavity, resilient cushions of ferrite impregnated material being positioned against opposite sides of the cavity for holding the magnet body in either of two stable positions.

9. A memory device for a conveyor comprising a housing attached to and carried by the conveyor, said housing having a cavity therein, said cavity having oppositely spaced arcuate end lobes and having opposite sides which reduce to a narrow center portion, and an elongated magnetic body positioned within the cavity and References Cited in the tile of this patent UNITED STATES PATENTS 2,784,851 Bretschneider Mar. 12, 1957 3,100,040 Kleist Aug. 6, 1963 FOREIGN PATENTS 1,614,932 Germany Aug. 29, 1957 1,102,449 Germany Mar. 16, 1961 

1. A MEMORY SYSTEM FOR A CONVEYOR COMPRISING A MAGNETIC BODY MOUNTED ON THE CONVEYOR ROTATABLE BETWEEN A FIRST STABLE POSITION AND A SECOND STABLE POSITION, MEANS ASSOCIATED WITH EACH PAIR OF SAID STABLE POSITIONS FOR APPLYING A FORCE TO THEIR ASSOCIATED MAGNETIC BODY TO TEND TO MAINTAIN SAID MAGNETIC BODY IN ONE OR THE OTHER OF SAID STABLE STABLE POSITIONS, MEANS POSITIONED IN SPACED RELATION TO THE CONVEYOR FOR MAGNETICALLY CO-ACTING WITH AND FOR SELECTIVELY CAUSING THE MAGNETIC BODY TO SHIFT FROM THE FIRST STABLE POSITION TO THE SECOND STABLE POSITION, AND SENSING MEANS POSITIONED IN SPACED RELATION WITH THE CONVEYOR FOR SENSING THE MAGNETIC BODY IN THE SECOND STABLE POSITION. 